A-listers including Justin Timberlake, Jennifer Lopez and Sarah Jessica Parker turned out to celebrate "the American woman" at a gala benefit in New York.

Hosted by US powerhouses Oprah Winfrey and Vogue editor-in-chief Anna Wintour, the annual Metropolitan Museum of Art's Costume Institute Gala Benefit also welcomed celebrity guests including country star Taylor Swift and actress Emma Watson. Many were accompanied by the designer who dressed them.

Oprah walked the arrival line with Oscar de la Renta, wearing a navy couture gown by the designer. She said she looked forward to going into the party and having a few shots of tequila.

Harry Potter star Emma took a break from studying for her final exams at Brown University to attend, wearing a white custom gown by Burberry.

"I'm pretty lucky I get the best of both worlds and that's why I'm so blessed," the teenager said.

When asked what goes on inside the Met Gala, Anna Wintour responded with a laugh: "Oh, we're very, very well behaved."

Lady Gaga was slated to perform at the ball but didn't walk the red carpet.

Instead, the famous face with the most unusual dress was singer Katy Perry. She wore a dress that literally lit up with LED lights.

"I feel like I really have to represent those girls that just go for it and do their own thing and, you know, have their own bit of spontaneity and self confidence," she said. "I think sometimes in fashion it can get a little stuffy so I wanted to lighten up!"